PSYA01 Final Exam Study Notes PDF

PSYA01 Final Exam Study Notes: **Chapter 1: The Discipline of Psychology** - It wasn't until careful scientific observations of Hungarian physician Ignaz Semmelweis in the 1840's that the link between handwashing and infection rates was established - Cannot rely on our own intuitions...

PSYA01 Final Exam Study Notes: **Chapter 1: The Discipline of Psychology** - It wasn't until careful scientific observations of Hungarian physician Ignaz Semmelweis in the 1840's that the link between handwashing and infection rates was established - Cannot rely on our own intuitions to provide an accurate or complete understanding of human mind and behaviour - **Introspection:** is the person observation of our own thoughts, feelings and behaviours - Because we are not perfect observers of the operations of our own minds, psychologists developed other methods that provide scientific insight into the mind (ex. MRI on humans when they are hungry vs. full, shows activity of brain) - Our greater sensitivity to bitter tastes is highly adaptive: most poisons or toxins tastes bitter, and if you want to stay alive, it is most important to avoid swallowing poison than to enjoy something sweet. Being far more sensitive to tastes that are bitter is to trait that has served our species well because it helps us avoid eating things that could kill us - Psychological scientists view the mind as a way of talking about the activities of the brain, including thought, emotion, and behaviour - The word *psychology* is a combination of two Greek words: *psyche* or "soul", and *logos* meaning "the objective study of." - Literally translated: Psychology means: "the objective study of the mind - Present day definition: the scientific study of behaviour, mental process, and brain functions- that is the scientific study of the mind - *Behaviour* refers to any action that we can observe - Although the bulk of psychology focuses on human behaviour, animal behaviour has been an essential part of the discipline, both for understanding animals better and for comparing and contrasting animal and human behaviour - Early efforts to study mental processes were generally unsatisfactory because they relied on the use of **introspection**, or the personal observation of your own thoughts, feelings, and behaviours. Because it is difficult for others to confirm your introspections, this subjective approach does not lend itself well to the scientific method. If you say that you are feeling hungry, how can anyone else know whether your observation is accurate? - Psychology is a relatively young discipline, dating back only to the 1870s - This psychology family tree includes two major roots: philosophy and the natural sciences - Both disciplines (philosophy and psychology) consider the relative balance of biological factors (nature) and environmental factors (nurture) in the resulting human behaviour. Both attempt to determine the relationships between self-interest and community welfare, between body and mind, and between humans and other species with which we share the planet. Although we typically consider questions of the unconscious mind and abnormal behaviour to be the realm of the psychologist, philosophers investigated these issues thousands of years before the first psychologist was born. - Running along a parallel track to the early philosophers, ancient physicians were laying the foundation of our biological knowledge of the brain and nervous system - Philosopher Aristotle believed that all knowledge is gained through sensory experience - Beginning in the 17th century, this idea flourished in the British philosophical school of *empiricism*. Empiricists, like John Locke, viewed the mind as a "blank slate" at birth, which then was filled with ideas gained by observing the world - Contemporary psychologists believe that experience interacts with inborn characteristics to shape the mind. Intelligence, for example, is influenced by both genetics and experience.  - Hermann von Helmholtz (1821--1894) asked his participants to push a button when they felt a touch. When a thigh was touched, participants reacted faster than when a toe was touched. Because the toe is farther from the brain than the thigh, signals from the toe required more time to reach the brain. - British empiricists: Knowledge is the result of experience - Ancient physicians: The brain is the source of the mind - 17^th^- and 18^th^ century natural sciences: Discoveries about sensation and movement showed that the mind was physical - Hermann von Helmholtz: Studies of reaction time reinforced the idea of the mind as physical - Gustav Fechner was able to identify the softest sound that a person could hear by randomly presenting sounds of different intensities to which a participant will respond "yes" or "no". When the "yes" responses reached 50%, Fechner concluded that the sound was within the range that the human ear could detect. Note: Fechner's research seemed very similar to Helmholtz's, note the importance of *mental processes* in Fechner's work as opposed to the simple measurement of physiology and Helmholtz experiment - William Wundt is considered the first experimental psychologist - Experiments reflected both his interests in consciousness and his training as a medical doctor - Believed that reaction time provided a measure of the amount of mental processing required to carry out a task, as his tasks became more complex, reaction time increased accordingly - Helmholtz was Wundt's mentor, former research to Helmholtz - Known as the first psychologist - First to believe that conscious experience could be studied scientifically, conducted first psychological experiment in his lab at the University of Leipzig in 1879 - Experiment:  How quickly after hearing a ball drop onto a platform could a person respond by striking a telegraph key? - Approach to psychology was known as **voluntarism**, which reflects this emphasis on conscious will and choice - One of Wundt's students, Edward Titchener (1867--1923), expanded on Wundt's views to establish a theory of **structuralism**, in which the mind could be broken down into the smallest elements of mental experience - Titchener believed that consciousness experience could be broken down into three types of mental elements: sensations, images, and feelings.  - John Wallace Baird who was born and raised in southwestern Ontario and obtained his undergraduate degree from the University of Toronto, spent a brief period at the University of Leipzig training under Wundt, before moving to Cornell University and completing his PhD under the supervision of Titchener - Gestalt Psychology: The structuralists' effort to break behaviour into its essential elements was rejected by a group of early 20th-century German psychologists, including Kurt Koffka, Max Wertheimer, and Wolfgang Köhler, who founded **Gestalt psychology** - *Gestalt* means "form" or "whole" - The Gestalt psychologists believed that breaking a "whole" perception into its building blocks, as advocated by the structuralists, would result in the loss of some important psychological information (think to "13" and "B" example, where visually they can look similar yet be perceived differently by others) - Focused on form perception - Gestalt Principles: Proximity (near one another, belongs together), Similarity (tend to group stimuli that are alike), Continuity (tend to continue points that results in straight or gently curved lines that create smooth paths), Closure (tend to ignore gaps in figures to create a sense of closure, or completeness), Simplicity (tend to organize and interpret forms in the simplest way possible) - In response to the publication of Charles Darwin's *The Origin of Species* in 1859 and *The Descent of Man* in 1871, functionalism emerged - **Functionalism** viewed behaviour as purposeful because it led to survival, instead of restricting themselves to exploring the structure of the mind, functionalists were more interested in why behaviour and mental processes worked in a particular way - William James' textbook *Principles of Psychology (1890)* - Coined the term *stream of consciousness* to describe the flow of ideas that people experience while awake - Throughout his discussions of mental processes and behaviour, James emphasized the role of evolution - For the functionalist, the value of an activity depended on its consequences. If we enjoy ice cream, it must be because eating sweet, high-fat foods enhances survival---at least it did for our ancestors, for whom famine was more of a problem than obesity - Behaviour= purposeful - While the structuralists were interested in *describing* conscious experience, the functionalists were more interested in *explaining why* we had such experiences - Sigmund Freud: built a bridge from his medical training as a physician to his belief in the impact of life experiences on behaviour - Freud's ideas about the existence of the unconscious mind, the development of sexuality, dream analysis, and psychological roots of abnormal behaviour influenced not just psychology, but also culture - developed the techniques of psychoanalysis for treating mental disorders - the work of S.F. on consciousness, sexuality, abnormal behaviour, and psychotherapy played a dominant role in psychology during the first half of the 20th century - Freud's methods were not scientific, theories based on observations of individual patients (primarily upper class Viennese housewives who were not typical of the human population) - Humanistic psychology: An approach that saw people as inherently good and motivated to learn and improve - Abraham Maslow contributed a theory of motivation and ideas about exceptional people to the growing humanistic psychology movement - Advice to parents to provide unconditional love to their children is a direct application of humanistic beliefs - When issues such as capital punishment arise, the humanistic contention that there are no bad people, just bad societies that fail people, typically appears as part of the debate - Humanistic therapists, like Carl Rogers (1902--1987), often rebelled against Freudian approaches to therapy - Behaviourists: - many behaviourists restricted their research to studies using animals - Armed with Darwin's evidence linking humans to animals, the behaviourists comfortably drew parallels between their observations of animals and their assumptions about human behaviour - Pavlov: while studying digestion of dogs, he realized that the dog's salivation in response of the arrival of the handler rather than just to the food itself, indicated the dog has associated (or linked) these signals with the arrival of food (referred to as Classical conditioning) - Freudians= humans are natural selfish and aggressive - Humanists= naturally good - Watson's legacy in psychology was enormous. He restricted psychology to the study of observable behaviour - Watson approached psychology with a focus on the relationships between environmental cues and behaviour - Edward Thorndike: proposed the *law of effect*, which suggested that behaviours followed by pleasant or helpful outcomes would be more likely to occur in the future, whereas behaviours followed by unpleasant or harmful outcomes would be less likely to occur - Like Thorndike, B.F Skinner was interested in the effects of consequences on how frequently behaviours were performed - Skinner shared Watson's belief that psychology did not benefit from consideration of consciousness or internal mental states - Generalized human behaviour to animal behaviour - Ulric Neisser gave the new field its name in his 1967 book, *Cognitive Psychology* (thinking, reasoning, and problem-solving - Cognition covers the private and internal mental processes that the behaviourists avoided studying---information processing, thinking, reasoning, and problem solving - Five Perspectives of Psychology: 1. Biological psychology (aka *behavioural neuroscience)*: focuses on the relationships between mind and behaviour and their underlying biological processes, including genetics, biochemistry, anatomy, and physiology 2. Evolutionary psychology: attempts to answer the question of how our physical structure and behaviour have been shaped by their contributions to our species' survival (extension of James' functionalism, also think of bitter taste example). our current behaviour exists in its present form because it provided some advantage in survival and reproduction to our ancestors 3. Cognitive psychology: focuses on the process of thinking, or the processing of information (focuses on retrieval and storage of memories) 4. Developmental psychology: explores the normal changes in behaviour that occur across the life span 5. Social and personality psychology: escribes the effects of the social environment, including social and **cultural diversity**, and individual differences on the behaviour of individuals. Social and personality psychologists recognize that we construct our own realities and that the social environment influences our thoughts, feelings, and behaviour 6. Clinical psychology: perspective seeks to explain, define, and treat psychological disorders. Many types of psychological disorders affect memory. Freud believed that traumatizing experiences were more difficult to remember, a process that he labelled *repression* **Chapter 2: The Measure of Mind: Methods of Psychology** - Scientists have concluded that there are multiple causes for stuttering. Many cases seem to have a basis in genetics - with stutterers showing more activation of the right hemisphere during speech -  A complete explanation of stuttering zooms back out to combine a predisposition for the problem resulting from genetics and biology with developmental, emotional, and social factors, like feeling embarrassed or anxious about speaking in front of peers - *Faith* is belief that does not depend on logical proof or evidence - The word  **science**  comes from the Latin  *scientia*, which means "knowledge." *Science* doesn't refer to just any type of knowledge, but rather to a special way of learning about reality through systematic observation and experimentation - **Objectivity** means that conclusions are based on facts, without influence from personal emotions or biases - This type of collective misremembering has been dubbed the "Mandela effect." (think to monopoly man example, and how rich man stereotype= having a monocle, and how we all thought he had one but he doesn't) - Our memories, and the conclusions that we draw from such memories, are prone to error and bias - The second important difference between science and everyday observations is the use of systematic as opposed to hit-or-miss observation. By "hit or miss," we mean making conclusions based only on whatever is happening around us. If we want to make conclusions about the human mind, we cannot restrict our observations to our immediate circle of acquaintances, friends, and loved ones. Our observations of the people we see frequently are probably quite valid. It's just that the people we know represent a small slice of the greater population. For example, we might be surprised to learn that our favourite candidate lost an election because "everyone we know" voted for that candidate - Finally, science relies on observable, objective, repeatable evidence, whereas everyday observation often ignores evidence, especially when it runs counter to strongly held beliefs and expectations - Many people are convinced that women talk more than men. If you hold this belief, you are likely to notice and remember instances that support your belief more than instances that contradict it. This difference in attention and memory is termed **confirmation bias**, and it represents one reason why objective and systematic observation are so important in scientific inquiries - Scientific method not linear, better portrayed as a loop - Science is never-ending, since we can never achieve complete certainty in our understanding of how the universe (or the human mind) functions - **Theories**, which are sets of facts and relationships between facts that can be used to explain and predict phenomena - The word *prediction* comes from the Latin words for "saying before." - The best scientific theories not only explain and organize known facts, but also generate new predictions  - How to develop and test a theory: Theoretical hypothesis (e.g. a causal mechanism or a mathematical equation) \> Testable prediction \> Confirmation \> Systematic observation (experimental or nonexperimental) - A **hypothesis** is a type of inference, or an educated guess, based on prior evidence and logical possibilities - A good hypothesis links concrete variables based on your theory and makes specific predictions - Scientists can only show when a hypothesis is fake, a false hypothesis must always be modified or discarded - Once you have a hypothesis, you are ready to collect the data necessary to evaluate it. The existing scientific literature in your area of interest provides considerable guidance regarding your choice of methods, materials, types of data to collect, and ways to interpret your data. - During this process, research undergoes **peer review**, in which it is scrutinized by other scientists who are experts in the same area. Only if other experts conclude that new research is important, accurate, and explained thoroughly will it be added to the existing body of scientific knowledge - **Replication:** repeating an experiment and getting the same results - During peer review, research that fits with existing knowledge is typically accepted more rapidly than work that is less consistent with previous reports. Results often undergo **replication**, which means that other scientists independently attempt to reproduce the results of the study in question (Klein et al., 2014). If the data are replicated, they will be accepted quickly. If other scientists are unable to replicate the data, their extra effort will have prevented inaccurate results from cluttering the scientific literature. Although this process might slow the publication of some innovative research, the result---more accuracy---is worth the effort - Psychological scientists use a variety of research methods, including descriptive, correlational, and experimental methods, depending on the type of question being asked. - Descriptive methods, including surveys, case studies, and observations, provide a good starting place for a new research question - Correlational methods help psychologists see how two variables of interest, like the number of hours spent on social media platforms and symptoms of depression, relate to each other. - Psychologists use experiments to test their hypotheses and to determine the causes of behaviour -  Constructs are internal attributes that cannot be directly observed but are useful for describing and explaining behaviour. Some examples of constructs include anxiety, intelligence, and extraversion - This process of taking an abstract construct and defining it in a way that is concrete and measurable is known as **operationalization** - **Descriptive methods** include case studies, naturalistic observations, surveys, focus groups, and interviews.  - **A case study** provides an in-depth analysis of the behaviour of one person or a small number of people - Many fields, including medicine, law, and business, use the case study method - Psychologists often use case studies when large numbers of participants are not available or when a particular participant possesses unique characteristics, as in the case described in this section. Interviews, background records, observation, personality tests, cognitive tests, and brain imaging provide information necessary to evaluate the case - Case studies are a useful source of hypothesis, but can also be used to test hypotheses - **Naturalistic observation**: If you are interested in learning about larger groups of people than are possible with the case study method, you might pursue **naturalistic observation**, or in-depth study of a phenomenon in its natural setting (think about Jane Goodall and her work with chimpanzees) - Some naturalistic observations are conducted when people know that they are being observed, while in other cases, people are unaware of being observed. Both situations raise challenges. If we know we are being observed, we might act differently. But watching people who do not know that they're being watched raises ethical issues - Like the case study method, naturalistic observation can be helpful for developing hypotheses, but other methods must be used to test them - **Surveys**, or questionnaires, allow us to ask large numbers of people questions about attitudes and behaviour. Surveys provide a great deal of useful information quickly, at relatively little expense - One of the primary requirements for a good survey is the use of an appropriate **sample**, or subset of a population being studied. The **population** consists of the entire group from which a sample is taken. Good results require large samples that are typical, or representative, of the population that we wish to describe - **Focus groups** and **interviews** are used to gather more detailed, nuanced information from research participants. In both interviews and focus groups, participants are asked to respond to specific questions or prompts, similar to the survey method. But unlike surveys, participants are not constrained to some preselected choice of response options. Rather, participants are free to provide any response they wish - Often, a researcher might use the survey method to gather initial information on a phenomenon from a large group of individuals, and then use the findings from the survey to develop prompts for use in interviews or focus groups - **Correlations** measure the direction and strength of the relationship between two **variables**, or factors that have values that can change, like a person's height and weight - Correlations begin by measuring our variables, a **measure** answers the simple question of "how much" of a variable we have observed - After we obtain measures of each variable, we compare the values of one variable to those of the other and conduct a statistical analysis of the results -  Three possible outcomes from the comparison between our two variables can occur: positive, negative, or zero correlation - In a positive correlation, high levels of one variable are associated with high levels of the other. Height and weight usually show this type of relationship - Two variables also can show a negative correlation, in which high values of one variable are associated with low values of another. For example, high levels of alcohol consumption among postsecondary students are usually associated with low GPAs - The third possible outcome is a zero correlation, in which the two variables have no systematic relationship with each other. When variables have a zero correlation, knowing the value of one variable does not tell us anything about the value of the other  - **A third variable**: is responsible for a correlation observed between two other variables of interest - If we cannot make conclusions about causality using correlations, why would we use them? In a number of circumstances, correlations are more appropriate than other research methods - Although this method will not allow us to conclude that stressful life events cause outcomes such as depression, we can at least identify the strength and direction (positive, negative, or zero) of any correlation between number of stressful life events and symptoms of depression - Experimental Methods: The scientist's most powerful tool for drawing conclusions about research questions is the formal **experiment** - Unlike correlational methods, the use of the formal experiment allows us to talk about cause - A good experimental design features random assignment of participants to groups, appropriate control groups, control of situational variables, and carefully selected independent and dependent variables. - A researcher begins designing an experiment with a *hypothesis*, which can be viewed as a highly educated guess based on systematic observations, a review of previous research, or a scientific theory. An experimental hypothesis takes this form: "If I do this, that will happen." To test the hypothesis, the researcher manipulates or modifies the value of one or more variables and observes changes in the values of others. The variable controlled and manipulated by an experimenter ("If I do this") is known as the **independent variable**. We need some way to evaluate the effects of this manipulation. We use a **dependent variable**, defined as a measure used to assess the effects of the manipulation of the independent variable, to tell us "what will happen" as a result of the independent variable. Like the independent variable, our choice of dependent variable is based on our original hypothesis. - To evaluate these irrelevant effects and establish a baseline of behaviour under the experimental conditions, we assign some of our participants to a **[control group]**. In many experiments, the control group will experience all experimental procedures except exposure to the independent variable. When a new treatment is being tested, the control group might experience the standard treatment for a condition. The experience of the control group should be as similar as possible to that of the **[experimental groups]**, who experience different values of the independent variable - individual differences among participants are an example of **[confounding variables]**, or variables that are irrelevant to the hypothesis being tested and can alter or distort our conclusions. For example, a researcher might want to test the effects of aerobic exercise on blood pressure. If some participants competed in triathlons without the researcher's knowledge, their athletic experience would confound the interpretation of the results - Limitations of experimental method: Experiments can be somewhat artificial. In the study described above, participants were asked to imagine that they were a part of this university Facebook group where this incident was taking place. Although this pretense is necessary in order to maintain a highly controlled setting, it also results in a rather artificial situation. Participants know that they are in a research study, and they may vary their behaviour as a result. However, making a laboratory experiment more realistic can raise ethical challenges. In a study conducted in 1962, before current ethical guidelines for research had been adopted, military personnel were led to believe that their lives were in danger so that experimenters could realistically assess the effects of panic on performance  - Independent (manipulated) and dependent (measured) - To conduct an experiment, we must carefully operationalize, or define our variables in practical terms - Psychologists have three specific techniques for assessing the normal behaviours associated with age: cross-sectional, longitudinal, and mixed longitudinal designs - Cross-sectional studies: An experimental design for assessing age-related changes in which data are obtained simultaneously from people of differing ages - *Cohort effects*, or the generational effects of having been born at a particular point in history (Any such cohort effects could mask or distort our cross-sectional results) - A method that lessens this dilemma is the **longitudinal study**, in which a group of individuals is observed for a long period (The longitudinal approach has few logical drawbacks but is expensive and time consuming. Participants drop out of the study because of moves or lack of incentive. Researchers then must worry about whether those who remain in the study still comprise a representative sample) - the **mixed longitudinal design**, combines the cross-sectional and longitudinal methods. Participants from a range of ages are observed for a limited time (usually about five years). This approach is faster and less expensive than the longitudinal method and avoids some of the cohort effects of the pure cross-sectional method - A valid measure actually measures what it is supposed to measure. In this case, your bathroom scale is supposed to tell you how much you weigh - **Validity** means that a measure leads to correct conclusions or evaluates the concept that it is designed to do - **Reliability** refers to the consistency of a measure - **Descriptive statistics:** Statistical methods that organize data into meaningful patterns and summaries, such as finding the average value - There are three types of measures for central tendency: the mean, median, and mode for each group of scores. The **mean** is the numerical average of a set of scores, computed by adding all the scores together and dividing by the number of scores - The **median** represents a halfway mark in the data set, with half of the scores above it and half below - The **mode** refers to the score that occurs most frequently, and it is easy to determine by looking at a histogram - The traditional way to look at the variance of scores is to use a measure known as the **standard deviation** - **Normal distribution:** 1. It is symmetrical 2. Its shape indicates that most scores occur near the mean, which is where measure of variability plays a role - Inferential statistics: Statistical methods that allow experimenters to extend conclusions from samples to larger populations, hey permit us to draw inferences or conclusions from data - Descriptive statistics allow us to talk about our sample data but do not allow us to extend our results to larger groups - To reach conclusions about how our observations of a sample might fit the bigger picture of groups of people, we use inferential statistics - inferential statistics can be powerful, we must be cautious about making **generalizations** from our results to larger populations. To generalize means to extend your conclusions to people outside your research sample - To ensure that a participant is a willing volunteer, researchers must make provisions for reasonable incentives. Incentives, such as pay or extra credit for participation, must not be so extreme that they become the primary motivation for prospective volunteers. To decide whether to volunteer for research, a person must have some knowledge of what the research will entail (informed consent) - Developmental psychologists have an obvious interest in children, but a person cannot sign a legal informed consent form until age 18. Can you obtain informed consent from a patient with schizophrenia, who suffers from hallucinations and irrational, delusional beliefs, or from a person in the later stages of Alzheimer's disease, whose memory and reasoning have deteriorated because of the condition? In these cases, legal permission must be obtained from a qualified guardian - Ethical guidelines for animal research require setting a clear purpose for the experiment, providing excellent care for the animals, and minimizing pain and suffering - In Canada and around the world, the "Three R's" tenet guides the use of animal research:  - *Replacement* refers to research methods that avoid or replace the use of animals in an area of research where they would have otherwise been used. - *Reduction* refers to any strategy that will result in fewer animals being used. - *Refinement* refers to the modification of animal care or experiment procedures to minimize pain and distress **Chapter 3: The Evolving Mind: Nature and Nurture Intertwined** - *Genes*, or segments of DNA that produce specific proteins, can be turned on and off. The genes that are not turned off are free to produce the proteins needed to build a particular kind of cell, whether that is a skin cell or a liver cell - Contemporary psychologists view the contributions of **nature** (our heredity or innate predispositions) and **nurture** (the results of our experience with the environment) as being closely intertwined, as opposed to somehow competing for control over structure and behaviour - Nature vs. Nurture was an idea proposed by Francis Galton (Charles Darwin's brother) - Galton believed that intelligence was largely the result of inheritance - Every nucleus in the approximately 37 trillion cells of your body, with the exception of your red blood cells and sperm or eggs, contains two complete copies of the human genome, a set of instructions for building a human - Your personal set of instructions is known as a **genotype**, which interacts with the environment to produce observable characteristics, known as a **phenotype** - One half of your genotype was provided by your biological mother's egg, and the other half was provided by your biological father's sperm. Each parent contributes a set of 23 chromosomes, which in turn are composed of many molecules of DNA. A smaller segment of DNA located in a particular place on a chromosome is known as a **gene**. Each gene contains instructions for making a particular type of protein. **Gene expression** occurs when these genetic instructions are used to produce a particular protein. Each cell contains the instructions for an entire human organism, but only a subset of instructions is expressed at any given time and location. Gene expression in a nerve cell is different from gene expression in a muscle cell or a skin cell - Different versions of a gene, or **alleles**, can give rise to different phenotypical traits. Many alleles can occur for a given gene, but an individual receives only two---one from each parent. For example, alleles for blood type include A, B, and O, but typically, nobody has all three - If both parents contribute the same type of allele, such as a version of the MC1R gene related to having freckles, the child would be considered **homozygous** for that gene (*homos* means "same" in Greek) - If the parents contribute different alleles, such as one for freckles from one parent and one related to not having freckles from the other, the child is **heterozygous** for that gene (*hetero* means "different" in Greek) - **Recessive** alleles determine a phenotype only when an individual is homozygous for a particular gene, whereas **dominant** alleles determine a phenotype in either the homozygous or the heterozygous condition - Genetic variation: The development of an egg or sperm cell is like shuffling a deck of cards - When a parent's cell divides to make an egg or a sperm cell, each resulting cell contains 23 chromosomes, one chromosome from each of the parent's original 23 chromosome pairs - **Relatedness** is defined as the probability that two people share copies of the same allele from a common ancestor - Of the 23 pairs of human chromosomes from each parent, 22 pairs are perfectly matched. In other words, a gene appearing on one of a pair of chromosomes (perhaps a gene for blood type) has a corresponding gene on its partner. In contrast, the X and Y chromosomes do not carry the same genes. The much-larger X chromosome contains about 2000 active genes, while the Y has fewer than 100 - However, individuals may also be born with a single sex chromosome (either X or Y) or three sex chromosomes (various combinations of X and Y). It is also possible for individuals to have two sex chromosomes but develop as the opposite sex - *Intersex* is an umbrella term used to describe individuals who are born with sex characteristics (including genitals, gonads, and chromosome patterns) that do not fit typical binary notions of male or female bodies - The allele responsible for hemophilia, a disease characterized by the failure of blood to clot, is found only on the X chromosome - The allele responsible for hemophilia, a disease characterized by the failure of blood to clot, is found only on the X chromosome. This allele is recessive, leading to different outcomes based on the sex of the child receiving the alleles. If a female receives a healthy allele on the X chromosome from one parent and a disease-causing allele on the X chromosome from her other parent, she will be a carrier for the condition but not experience it.  In contrast, a male receiving a disease-causing allele on the X chromosome from his mother will have the condition - If a daughter inherits her mother's X chromosome containing the allele for hemophilia , she will be a carrier but will not have the disease. If a son inherits this  chromosome, he will have the disease. Unlike his sister, he does not have a healthy X chromosome to offset the disease allele. - Even when genes are duplicated on the X and Y chromosomes, they can perform very differently depending on their location - Our species shares quite a few genes with chimpanzees, mice, fruit flies, yeast, and a weed known as *thale cress* - the *FoxP2* gene, which appears to be responsible for spoken language - **Behavioural genetics** investigates the strength of genetic influences on a particular behaviour. **Heritability** is the statistical likelihood that variations observed across individuals in a population are due to genetics - **Concordance rates:** The statistical probability that a trait in one person will be shared by another; usually discussed in relation to identical and fraternal twins - Although we can say that all humans share 100 percent of their genes, we do not share 100 percent of our alleles, giving each of us a unique version of the genome. In other words, we all share genes that produce eye colour of some sort, but our different combinations of alleles result in a variety of shades - It is important to remember that genes encode for proteins, not behaviours. Genes build proteins that construct brains, and brains might or might not become addicted to cannabis. Rather than viewing a gene as causing a complex behaviour, it is more accurate to view genes as contributing to the development and functioning of the nervous system, which in turn generates observable behaviour - Instead, **candidate gene** research studies were conducted, in which one gene or a small number of genes were compared between groups of people with and without a condition of interest - Having identical genotypes, as is the case with identical twins, does not guarantee identical phenotypes, or observed characteristics - **Genotype**: an individual's genetic makeup - **Phenotype**: an individual's observable trait - **Gene**: A sequence of DNA in a specific location on a chromosome that contains the instructions for making a protein - **Gene expression**: Introduction from a gene is used to produce a protein - **Allele**: One of two or more possible variations of a gene - **Homozygous**: Having two of the same alleles - **Heterozygous**: Having two different alleles - **Dominant:** An allele is expressed regardless of whether it is homozygous or heterozygous - **Recessive**: An allele that is expressed only when it is homozygous - different phenotypes can result from the same genotype due to interactions between the organism and its environment. When factors other than the genotype produce changes in a phenotype, we say that an **epigenetic** change has occurred - *Epi* is Greek for "over" or "above," so *epigenetics* refers to the reversible development of traits by factors that determine how genes perform - Epigenetic change influences *gene expression*, the process by which DNA builds proteins that contribute to features of living cells. Genes can be turned on or off by internal signals (hormones or neurochemicals) or by signals from external sources (diet or toxins). There is an obvious need for epigenetics in development, as the differences between a skin cell and a muscle cell result from turning on the right set of genes and turning off others. Thus, the magnitude of epigenetic change depends on an organism's age. The fetus experiences the highest rate of epigenetic change, followed by the child and finally, the adult. While epigenetic changes are reversible, many last entire lifetimes. For example, individuals who experienced traumatic life events during childhood were found to have long-term epigenetic changes in the hippocampus, a structure associated with memory and responses to stress - Among the factors known to produce epigenetic change are nutrition, disease-causing organisms, drugs, stress, and environmental toxins - you will see that many disorders trace their roots to a combination of genetic vulnerability and disruptions experienced by the pregnant woman, such as illness or malnourishment - Geneticists have identified four processes that produce lasting but reversible changes in gene expression: ribonucleic acid (RNA) interference, RNA editing, histone modification, and DNA methylation  - DNA methylation occurs when a methyl group (one carbon atom bonded to three hydrogen atoms) is added to the DNA molecule. This has the result of turning genes off. You can think about DNA *methylation* as being similar to stapling some pages in a book together. Because of the staples, you can't read the pages - Two processes for producing epigenetic change are histone modification and DNA methylation. Histone modification occurs when certain chemicals interact with the tail or core of a histone. DNA methylation occurs when a methyl group (one carbon atom bonded to three hydrogen atoms) attaches to the DNA molecule. These modifications affect the likelihood that particular genes will be expressed or silenced - Although many epigenetic studies examine physical features like fur colour, more complex features of interest to psychologists are also subject to epigenetic influences. For example, rats that were licked frequently during infancy by their mothers (the rat equivalent of getting a hug from mom) were calmer when faced with stress later in life than rats licked infrequently - In contrast, patterns of DNA methylation and unusual histone modifications are strongly associated with risk for these conditions - Many common foods have known epigenetic effects. Intake of garlic, broccoli, and dietary fibre can turn on anti-cancer and other protective genes. We saw earlier in this chapter how mother mice exposed to BPA gave birth to offspring that had yellow fur and were obese due to reduced methylation of the Agouti gene. However, if the mother exposed to BPA was also given a diet rich in the nutrients choline, betaine, and vitamin B12, all of which contribute to increased methylation, the offspring had normal weight and brown fur. We might not be able to control the environmental toxins to which we are exposed, but a greater understanding of epigenetics might help balance our exposure with appropriate nutrition. - The human genome is the product of millions of years of **evolution**, defined by biologists as descent with modification from a common ancestor - Evolution can result from mutation, migration, and genetic drift - A **mutation** is an error that occurs when DNA is replicated. The average human baby is born with about 130 new mutations, but most have no effect (Zimmer, 2009). Mutant alleles providing some advantage spread through the population, but most mutant alleles that result in a disadvantage disappear from future generations - **Migration** occurs when organisms move from one geographical location to the next. Moving to a new location can affect the survival of individuals and the frequency of certain alleles in the population. Phenotypical traits that are advantageous in one environment might be less so in another - **Genetic drift** produces change from one generation to the next through chance or accident. Type B blood is virtually absent in contemporary populations of Indigenous North American peoples, most likely due to chance - **Fitness:** the ability of one genotype to reproduce more successfully relative to other genotypes - Natural selection favours the organism with the highest degree of **fitness**, defined as the ability of one genotype to reproduce relative to other genotypes - The concept of fitness includes survival to adulthood, ability to find a mate, and reproduction - *fitness* describes the interaction between characteristics and the environment in which they exist - **Adaptation** refers to either the process or the result of change because of natural selection. In other words, a species can respond to an environmental change by adapting, and features of the new phenotype may be called *adaptations*. Adaptations can take many forms. They can be behaviours, such as jumping higher to better avoid a predator, or anatomical features, such as eyes that can see colour. Adaptations do not necessarily produce perfection. Any adaptation that is good enough to contribute to the fitness of an organism will carry forward into future generations - In these primitive animals, the nerves in the abdomen were as likely to be important to behaviour as the ones in the head - the most unique area of the human brain is the cerebral cortex, the outermost layer of the brain. Compared with other primates, the human brain has a much larger cerebral cortex. - The major factor distinguishing human intelligence from intelligence of other species is the richness and complexity of the social behaviour supported by the human brain. Managing the abilities to distinguish friend and foe, imitate the behaviour of others, use language to communicate, recognize and anticipate the emotions, thoughts, and behaviour of others, maintain relationships, and cooperate required the evolution of a special brain - It is possible that we have reached equilibrium between our needs for intelligence and the costs of a big brain. Brains are expensive to run in terms of nutrients. Although the brain comprises only about 2 percent of the body's weight, it requires at least 15 percent of the body's resources. In addition, brain size may be limited by the dimensions of the birth canal. - The evolutionary psychology approach not only owes an obvious debt to Darwin, but also is a direct descendant of the functionalism supported by William James. As the term *functionalism* implies, behaviour is seen as promoting survival, as opposed to being random and pointless. The goal of evolutionary psychology is to explain how the patterns of behaviour that we share with other humans have been shaped by evolution - Finally, in **altruism**, one individual's self-sacrifice is designed to benefit another individual (Honeybees sting to defend their hive, but in doing so, they end their own lives) - Among emperor penguins (*Aptenodytes forsteri*), survival of the chicks in the hostile Antarctic cold depends not only on an individual parent, but on the larger huddle formed by other parents - Sacrificing your life to save a close blood relative might increase the likelihood that your alleles would be passed along to subsequent generations. Self-sacrifice in this case does not need to be a conscious decision. Any behaviour that results in a greater frequency of the relevant genes in subsequent generations will become more common - Because males have a lower investment of time and resources in reproduction compared to females, it might seem that the best reproductive strategy for males would be promiscuity, but this is not usually the case. In species such as our own, with lengthy and complex development leading to adulthood, a male who abandons his offspring puts their survival at risk (Gibson, 2008). Even if a man fathers many children, his genes are less likely to make it into the next generation if most or all perish from lack of care or protection - The mother can maximize her children's chances of survival by choosing a father who will not only pass along healthy genes, but also participate in the raising of children - Sexual selection might occur in two ways: - In intrasexual selection (*intra* means "within"), members of one sex compete with one another for access to the other sex. In some species, such as deer, males engage in fights that determine which males are allowed to mate and which are not. Features like large antlers, which assist in winning a fight, could become sexually selected - In intersexual selection (*inter* means "between"), characteristics of one sex that attract the other might become sexually selected. The male peacock's luxurious tail appears to have developed for the sole purpose of attracting mates - Evolutionary psychologists have argued that a number of human traits might have been subjected to sexual selection, including humour and vocabulary. According to this argument, human males use humour and their vocabularies to impress females with their intelligence because of intersexual selection - We can also tell you about one behaviour that does not successfully attract females---taking unnecessary risks- However, risky activities might have indirect positive outcomes for males. Dominant, successful males are likely to attract more females, and dominance among males is often decided on the basis of intrasexual competition in risky endeavours **Chapter 4:** - ** **Social exclusion not only separated a person from the help of others in life-threatening situations, perhaps in fending off a predator, but worse, could lead to outright conflict with others, including combat - Under such hostile circumstances, socially excluded people faced a greater risk from bacterial infections than from viruses. Bacteria enter the body through cuts and scratches, whereas viruses are transmitted through body fluids (e.g., sneezing), so you are most likely to be exposed to them when you are in close contact with other people - Her brain will respond to her feelings of isolation by generating hormonal signals that will tell her immune system (shown in the larger image at the beginning of the chapter) to gear up to protect her against bacteria - In contrast, if she usually feels socially connected to others, her brain will initiate a cascade of hormonal signals that tell her immune cells to prepare to protect her against viruses - This is just one example of how the mind's perceptions of the social environment---whether it is friendly or not, for instance---can affect biological processes that are important to health and survival. - Such ideas led thinkers like Renaissance philosopher René Descartes to propose a philosophy of dualism, which suggests that our mind is somehow different and separate from our physical being - Biological psychology, also known as behavioural neuroscience, is the scientific study of the reciprocal connections between the structure and activity of the nervous system and behaviour and mental processes - Biological changes often influence behaviour and cognition. For example, when your stomach is empty, a gut hormone called ghrelin is released. When ghrelin reaches the brain, you respond by feeling hungry. After you eat, ghrelin release is suppressed and you feel satisfied, so biology (amount of ghrelin released) initiates behaviour and cognitions (feeling hungry and beginning to eat, or feeling full and stopping eating) - One thing phrenologists got right: Their notion that some behavioural functions are localized to certain areas of the brain is one we share today - CNS= central nervous system (brain and spinal cord-form one continuous unit of tissue) - Nerves branch outward from the CNS to all areas of the body---the lungs, heart, and other organs; the eyes and ears; and the arms, legs, fingers, and toes - PNS= peripheral nervous system - As soon as a nerve branches outward from the CNS, it is considered part of the PNS - Another way to know you have left the CNS for the PNS is to look for the protection of bone. Nerves of the CNS are encased in bone, but those of the PNS are not Peripheral Nervous System (PNS): Parts and Function - Neurons (nerve cells), humans have 100 billion of them - the nervous system contains many supporting cells, known as glia - Neural communication is a two-step process. The first step takes place within a single neuron and involves the generation of an electrical signal. The second step takes place between two neurons and involves the release of a chemical messenger from one neuron that affects the activity of the second - Like other cells, a neuron has a large central mass or **cell body**, and within the cell body, it has a nucleus -  Most housekeeping tasks of the cell, such as the translation of genetic codes into the manufacture of proteins, take place in the cell body. Like other cells, neurons feature an outer membrane, which surrounds the neuron and forms a barrier between the fluid outside the cell (the extracellular fluid) and the fluid inside the cell (the intracellular fluid). The neural membrane is composed of fatty materials that do not dissolve in water, so even though it is only two molecules thick, it is able to hold apart the water-based fluids on either side. Pores within the membrane act as channels that allow chemicals to move into or out of the cell - The branches known as **axons** are responsible for carrying information to other neurons, while the branches known as **dendrites** receive input from other neurons - At its farthest point from the cell body, an axon bulges to form a terminal. If you look inside an axon terminal with an electron microscope, you can see round, hollow spheres known as synaptic vesicles, which contain molecules of chemical messengers - When we prepare neural tissue for study using microscopes, the chemicals used to preserve the tissue are absorbed by cell bodies. This gives cell bodies a pink--grey colouring. In contrast, these chemicals are repelled by the insulating material covering most axons because the insulation has a fatty composition that doesn't mix well with the watery preservatives (we discuss the nature of this insulation shortly). As a result, axons look white, like the fat in a steak. When we examine images of the brain, areas that look grey have a high density of cell bodies, whereas areas that look white consist of large bundles of axons - Some glia (from the Greek word for "glue") provide a structural matrix for neurons, ensuring that the neurons stay in place - Other glia are mobile, allowing them to move to a location where neurons have been damaged to clean up debris - Glia form tight connections with the blood vessels serving the nervous system - n vertebrates such as humans, glia wrap around some axons, forming an important layer of insulation called **myelin**. Myelin makes neural signalling fast and energy efficient - By speeding up the transmission of neural signals and contributing to quicker recovery between signals, myelin increases the amount of information a neuron can transmit per second by a factor of 3000 times - Glia in the brain and the spinal cord form scar tissue, inhibiting repair to the damaged nerves. Because of this feature, we consider damage in the CNS to be permanent -  In contrast, damaged glia in the PNS do not form scar tissue and instead help the damaged axons regrow. As a result, nerve damage in these areas can heal - myelin growth in the human nervous system begins before birth, but it is not completed until early adulthood, possibly as late as age 25. The last area of the nervous system to be myelinated is the prefrontal cortex, which is involved with judgment and morality - Until myelin in this area is mature, these neurons do not work as efficiently, which is one of the possible reasons teenagers and adults sometimes make different decisions - Neural communication is a two-step process. In the first step, which takes place in the signalling neuron's axon, the neuron generates an electrical signal known as an **action potential**. This signal travels the length of the axon from its junction with the cell body to its terminal. In the second step, which takes place between two neurons, the arrival of an action potential at the axon terminal of the first neuron signals the release of chemical messengers, which float across the extracellular fluid separating the two neurons. These chemicals influence the likelihood that the second neuron will respond with its own action potential, sending the message along - When a neuron is not processing information, we say that it is at rest. When a cell is at rest, the difference between the readings from the interior of the axon and the external fluid is known as the **resting potential**. - Neurons can respond to incoming chemical signals by becoming either depolarized or hyperpolarized. The word *polarized* means "far apart," such as when political factions disagree. Being depolarized means we have moved closer together, and being hyperpolarized means we have moved even farther apart than before. In the case of neurons, depolarization means that the difference between the electrical charges of the extracellular and the intracellular recordings is decreasing. Hyperpolarization means that the difference is increasing - When a neuron is depolarized by sufficient input, it reaches a threshold for producing an action potential. A threshold is the point at which an effect, the action potential in this case, is initiated. Once this threshold is reached, the generation of an action potential is inevitable. Approaching the threshold for initiating an action potential is similar to pulling the trigger of a gun. As you squeeze the trigger, nothing happens until you reach a critical point. Once that critical point is reached, the gun fires, and there is nothing you can do to stop it - Reaching threshold initiates a sequence of events that reliably produces an action potential (see Figure 4.7). These events involve the opening and the closing of pores or channels in the neural membrane, which in turn allow certain chemicals to move into and out of the cell. These chemicals are in the form of ions or electrically charged particles dissolved in water. When threshold is reached, channels open, allowing one type of ion, sodium, to rush into the neuron - Near the peak of the action potential, channels open that allow another type of ion, positively charged potassium, to move across the membrane. Potassium begins to leave the cell. As the interior loses these positively charged potassium ions, our recording heads in the negative direction again. Following the production of the action potential, the neuron requires a time-out or refractory period, during which it returns to its resting state. During this refractory period, the cell is unable or unlikely to respond to further input by producing another action potential. - Either an action potential occurs, or the cell remains at rest---there is no middle ground-action potentials are all or none - Action potentials do not affect the entire axon all at once. The process we just described takes place first in a small segment of the axon where the axon connects to the cell body. The next step is propagation, or the duplication of the electrical signal down the length of the axon to the axon terminal, where it initiates the release of chemical messengers - Propagation takes place differently in myelinated and unmyelinated axons. In an unmyelinated axon, action potentials occur step by step, from one small section of the axon to the next adjacent section, down the entire length of the axon. In contrast, action potentials in myelinated axons are formed only at the sections of the axon membrane between adjacent segments of myelin, known as nodes of Ranvier. In other words, propagation in myelinated axons can "skip" the sections covered by myelin - The more action potentials it takes to move a signal down the length of the axon, the more energy is expended returning the cell to its resting state - Propagation in myelinated axons is fast and efficient (see Figure 4.8). After an initial action potential is generated near the cell body, the current flows beneath a segment of myelin until it reaches a node of Ranvier, where another action potential occurs. Like the express bus, the action potentials skip the myelinated sections of the axon, reaching their destination, the axon terminal, about 20 times faster than if the axon were unmyelinated. By covering the same distance with fewer action potentials, the myelinated axon uses less energy returning to the resting potential than an unmyelinated axon would need - Once the action potential reaches the axon terminal, the neural communication system switches from an electrical signalling system to a chemical signalling one - The point of communication between two neurons is known as a **synapse** - Instead, they are separated by tiny gaps filled with extracellular fluid. Because electrical signals are unable to jump this gap, neurons send chemical messengers instead - Neurotransmitters: Acetylcholine (Ach), Epinephrine The neurotransmitters in the axon terminal are contained in synaptic vesicles. The arrival of an action potential releases the vesicles from their protein anchors, much like boats leaving a dock, and the vesicles migrate rapidly to the cell membrane. Because the vesicles are made of the same thin, oily material as the membrane, they easily fuse with the membrane and spill their contents into the synaptic gap, similar to popping soap bubbles in a bathtub. Following release, the vesicles are pinched off the membrane and refilled. (adrenaline), Norepinephrine (noradrenalin), Dopamine, Serotonin, Glutamate, GABA, Endorphins - The neurotransmitters released across the synaptic gap come into contact with special channels on the receiving neuron, known as receptors. **Receptors** work with the neurotransmitters like locks and keys. Only a neurotransmitter with the right shape (the key) can attach itself or bind to a particular receptor (the lock). Neurotransmitters do not stay bound to receptors long. Once they pop out of the receptor binding site, neurotransmitter molecules drift away from the gap, are broken down by enzymes, or return to the axon terminal from which they were released in a process called reuptake. In **reuptake**, special channels in the axon terminal membrane known as transporters allow the neurotransmitters to move back into the releasing neuron where they are repackaged for later use - The interaction between neurotransmitters and their receptors can have one of two effects on the receiving neuron: excitation or inhibition. When a neurotransmitter has an excitatory effect, it slightly depolarizes the receiving neuron, increasing the likelihood that the neuron will reach threshold and initiate an action potential. Recall that depolarization reduces the difference between the electrical environments inside and outside the neuron. When a neurotransmitter has an inhibitory effect, it slightly hyperpolarizes the receiving neuron, moving the cell farther from threshold and reducing the likelihood that it will initiate an action potential. Recall that hyperpolarization increases the difference between the electrical environments inside and outside the neuron. - **Agonists** are drugs that enhance the actions of neurotransmitters, and **antagonists** are drugs that inhibit the actions of neurotransmitters - An agonist might enhance the actions of a particular neurotransmitter by increasing its release, blocking its reuptake, or by mimicking the neurotransmitter and activating its postsynaptic receptor - In contrast to an agonist, an antagonist might inhibit the actions of a particular neurotransmitter by blocking its release, destroying the neurotransmitter in the synapse, or by mimicking the neurotransmitter and binding to a postsynaptic receptor in a way that prevents neurotransmitter binding. For example, beta blockers, a class of drugs commonly prescribed to individuals who have suffered a heart attack, are antagonists that block certain receptor sites for epinephrine and norepinephrine, weakening the effects of the sympathetic stress response - f there is sufficient depolarization to reach threshold at this junction, the neuron generates an action potential. If not, it remains at rest - The neuron's "decision" to generate an action potential or not is called summation; the neuron is adding up all incoming messages and making a decision based on that information - Acetylcholine (ACh) is a neurotransmitter found in many systems important to behaviour. ACh is found at the neuromuscular junction, the synapse at which the nervous system commands muscles. Interference with the action of ACh at the muscles can result in paralysis and death - ACh also serves as a key neurotransmitter in the autonomic nervous system which carries commands from the brain to the glands and organs - ACh is also intimately involved in the brain circuits related to learning and memory - Norepinephrine activity in the brain leads to arousal and vigilance. Consistent with this role in arousal, norepinephrine is also released by the sympathetic nervous system. - Dopamine is involved with systems that govern movement, planning, and reward - Dopamine participates in the brain's reward and pleasure circuits by becoming active whenever we engage in behaviours that promote survival and successful reproduction, such as eating a great meal or having sex - Serotonin is involved with systems regulating sleep, appetite, mood, and aggression - Endorphins, short for endogenous morphine or morphine produced by the body, modify our natural response to pain - In evolutionary terms, it makes sense to have a system that reduces your chances of being disabled by pain during an emergency. All too frequently, however, we underestimate the extent of our injuries until we wake up the next morning feeling sore - In other words, the opioid drugs are so similar in chemical structure to our natural endorphins that the receptors cannot tell them apart and treat the opioids as if they were natural endorphins -  adult neurogenesis does occur, and that new neurons are continuously generated by stem cells in two regions of the adult mammal (including human) brain: the hippocampus (a subcortical region of the brain described later in this chapter) and the olfactory bulb (a region located above the nasal cavity and involved in the sense of smell - **Neuroplasticity** refers to the ability of neurons to change in structure and function in response to alterations in their environment. Newly generated neurons enjoy a brief period of enhanced plasticity, and neurons generated by the adult brain may play a critical role in experience-induced plasticity - The brain and the spinal cord are among the best protected parts of your body, which is not surprising given their importance for your survival. Surrounding the brain and the spinal cord are the heavy bones of the skull and spinal vertebrae - Meningitis is the inflammation of the membranes ("meninges"-under these bones, membranes known as "meninges" provide further protection - The brain and the spinal cord are further protected by a clear, plasma-like fluid known as cerebrospinal fluid (CSF)) covering the brain and the spinal cord - Near the base of the skull, openings enable CSF to flow from the ventricles into a space within the meninges, allowing the fluid to flow around the outer surfaces of the brain and spinal cord. CSF is constantly produced, so blockages in its circulation cause the fluid to build up. The result is hydrocephalus, which means "water on the brain." - To diagnose some medical conditions, it is helpful to obtain a sample of CSF. This is done through a spinal tap, in which a physician removes some of the CSF circulating through the meninges surrounding the spinal cord - The spinal cord serves as a major conduit for information flowing to and from the brain along large bundles of nerve fibres, carrying sensory information from the body and delivering commands to muscles - Neurons that have neither sensory nor motor functions are called interneurons. *Inter* in this case means "between," because many interneurons form bridges between sensory and motor neurons - Most sobriety tests assess the function of the cerebellum, which helps us maintain balance and muscle coordination - The brainstem contains structures responsible for reflexive behaviours, heart rate, breathing, arousal, sleep, preliminary sensory analysis, balance, and movement - The spinal cord merges with our first brainstem structure, the **medulla**. Like the spinal cord, the medulla contains large bundles of nerve fibres travelling to and from higher levels of the brain. The medulla manages many functions essential to life, such as heart rate, breathing, and blood pressure - Just above the medulla is the **pons**, which contains structures involved with the management of sleep, arousal, and facial expressions. *Pons* means "bridge" in Latin. The pons not only serves as a bridge between the higher and lower portions of the brain, but it also connects the **cerebellum** to the rest of the brain - Essential for maintaining balance and motor coordination, the cerebellum is one of the first structures in the brain to be affected by alcohol - Surprisingly, the cerebellum contains more nerve cells than the rest of the brain combined. Not only does the cerebellum contain huge numbers of neurons, but it is also richly connected with the rest of the CNS - Damage to the human cerebellum produces subtle deficits in language, cognition, and perception - The **midbrain** sits above the pons and contains a number of structures involved in sensory reflexes, movement, and pain - he periaqueductal grey of the midbrain plays an important role in the body's management of pain because it contains receptors for endorphins, our natural opioids - the periaqueductal grey of the midbrain plays an important role in the body's management of pain because it contains receptors for endorphins, our natural opioids - When endorphins are present in the periaqueductal grey, they reduce the perception of pain by decreasing the strength of pain messages traveling to higher levels of the brain. Nearby are other cell clusters that serve as the major sources of two important chemical messengers in the brain, serotonin and norepinephrine. These structures participate in states of arousal, mood, appetite, and aggression - The **reticular formation**, which participates in the management of levels of arousal - The cells in the reticular formation have two settings---fast and slow. When the cells are firing quickly, we usually show other signs of being awake. When the cells are firing slowly (or are damaged due to a stroke or other injury), an individual will enter either deep sleep or unconsciousness - Almost at the centre of the brain lies the **thalamus**. The thalamus is often called the gateway to the cortex, because input from most of our sensory systems (vision, hearing, touch, and taste) travels first to the thalamus, which then forwards the information to the cerebral cortex - The cortex, in turn, forms large numbers of connections with the thalamus - he thalamus is involved with memory and states of consciousness, Lesions in the thalamus are associated with profound memory loss - The basal ganglia also contribute to several psychological disorders, including obsessive-compulsive disorder (OCD) and attention deficit hyperactivity disorder (ADHD). These disorders are characterized by inadequate control of voluntary movement. In the case of OCD, patients may endlessly repeat a behaviour, such as hand-washing, while in ADHD, voluntary movements can be unusually frequent, rapid, and impulsive - The **hypothalamus** is involved with motivation and homeostasis or the regulation of body functions such as temperature, thirst, hunger, biological rhythms, and sexual activities - The hypothalamus is often described as contributing to the "4F" behaviours: feeding, fleeing, fighting, and, well, sex (fornication) - The hypothalamus carries out its motivational and homeostatic tasks by directing the autonomic nervous system and the endocrine system and its hormones - The **hippocampus**, named for its shape after the Greek word for seahorse, is essential to the formation of long-term memories, which we discuss in more detail in Chapter 9. Memories are not stored permanently in the hippocampus, but it is likely that the hippocampus is involved in the storage and retrieval of memories located elsewhere in the brain. Damage to the hippocampus results in profound impairments in the ability to form new memories, but intelligence, personality, and most memories of events that occurred before hippocampal damage remain intact - The **cingulate cortex** forms a fold of tissue on the inner surface of each cerebral hemisphere. The forward two thirds of this structure, known as the anterior cingulate cortex (ACC), participate, along with the hypothalamus, in the control of the autonomic nervous system. The t also plays significant roles in decision making, emotion, anticipation of reward, and empathy. The rear third, or posterior cingulate cortex (PCC), participates in memory and visual processing - The amygdala receives sensory information (vision, hearing, and smell) and produces emotional and motivational output that is sent to the cerebral cortex - Although the amygdala responds to both positive and negative stimuli, it is best known for its role in identifying, remembering, and responding to fear and aggression - bove the brainstem, we find the two large cerebral hemispheres, which are connected by a large bundle of nerve fibres known as the **corpus callosum**. The thin layer of cells covering the outer surface of the cerebral hemispheres is the **cerebral cortex** - Most of the remaining bulk of the hemispheres is made up of white matter, or nerve fibre pathways, that connects the cortex with other parts of the nervous system - As species' behaviour becomes more complex, we see a corresponding increase in the degree of convolution (wrinkling) of the cerebral cortex - Toward the front of the brain, we find the **frontal lobe**, and directly behind the frontal lobe lies the **parietal lobe**. At the back of the brain is the **occipital lobe**. Curving around the side of each hemisphere, we find the **temporal lobe**. Because we have two hemispheres, it follows that we have pairs of each type of lobe, usually denoted right or left (e.g., right frontal lobe and left frontal lobe) - The functions performed by different areas of the cerebral cortex within the lobes fall into three categories: sensory, motor, and association - The primary visual cortex is in the occipital lobe, and the primary auditory cortex is in the temporal lobe. The primary somatosensory cortex (*soma* refers to "body") is in the parietal lobe and processes information about touch, pain, body position, and skin temperature. The primary motor cortex is in the rearmost portion of the frontal lobe and provides the highest level of voluntary control over movement. Areas of the cortex that do not have specific sensory or motor functions are known as association cortex. *Association* means "connection" in this case, and association cortex helps us form bridges between sensation and action, language, and abstract thought - Broca's area participates in the production of speech - Consequently, damage to Broca's area caused by a stroke or a tumour produces considerable difficulty in speaking, although comprehension of speech remains good - The most forward portion of each frontal lobe, known as the **prefrontal cortex** (*pre* means "before"), is involved with the planning of behaviour, attention, and judgment. **Executive functions** refer to the range of cognitive processes that enable self-regulation and the cognitive control of behaviour, including attentional control, inhibition, planning, and self-monitoring - Knowing the outcome of the Gage case, you might be astonished to learn that physicians in the 1940s and 1950s deliberately damaged the frontal lobes of nearly 50 000 American patients in a procedure known as a frontal lobotomy. The intent of the procedure was to reduce fear and anxiety in patients with serious psychological disorders, which it accomplished in many cases but at great expense to the patient - The **orbitofrontal cortex**, a part of the prefrontal cortex located just behind the bony orbits protecting the eyes, plays an important role in our emotional lives - People with damage to the orbitofrontal cortex demonstrate dramatic deficits in their social behaviour and experience of emotion, despite retaining their intelligence, language skills, and abilities to pay attention, learn, and remember - The primary visual cortex begins the process of interpreting input from the eyes by responding to basic information about an image, such as its borders, shading, colour, and movement - Two important pathways link the occipital lobe with the rest of the brain. A pathway connecting the occipital lobe with the temporal lobe allows you to recognize objects you see. A second pathway connects the occipital lobe with the parietal lobe and allows you to process the movement of objects - The temporal lobe is home to the primary auditory cortex, which allows us to process incoming sounds - The temporal lobe has several areas that are specialized for particular functions. The temporal lobe is home to the primary auditory cortex, which allows us to process incoming sounds. As mentioned earlier, the temporal lobe processes some higher visual system tasks, including the recognition of objects and the faces of familiar people. Patients with damage to the temporal lobe are often unable to recognize their loved ones by sight. They must wait until the person speaks - The parietal lobe is home to the primary somatosensory cortex, which helps us localize touch, pain, skin temperature, and body position. Damage to the parietal lobe can produce the odd symptoms of neglect syndrome. Patients with this condition have difficulty perceiving part of their body or part of the visual field - Movement and sensation on the right side of the body are processed by the left hemisphere, and movement and sensation on the left side of the body by the right hemisphere - **Autonomic Nervous System**: The division of the peripheral nervous system that directs the activity of glands, organs, and smooth muscles - The autonomic nervous system contains three subdivisions: the sympathetic, the parasympathetic, and the enteric - **sympathetic nervous system** prepares the body for situations requiring the expenditure of energy, while the **parasympathetic nervous system** directs the storage of energy - The **enteric nervous system**, shown in Figure 4.27, consists of nerve cells embedded in the lining of the gastrointestinal system. This system is often called a "second brain" because it contains as many nerve cells as are found in the spinal cord - The enteric nervous system communicates with the endocrine system, to ensure the release of chemicals essential to digestion - he enteric nervous system is the source of 95 percent of the body's serotonin, a neurochemical discussed earlier in this chapter **Chapter 5: The Perceiving Mind: Sensation and Perception**: - The rods and cones in the retina begin the process of interpreting the light energy that enters the eye - The process of **sensation** brings information to the brain that arises in the reality outside our bodies, like a beautiful sunset, or originates from within, like an upset stomach - Sensory systems have been shaped by natural selection, to provide information that enhances survival within a particular niche - Differences in sensation do occur from person to person, such as the need to wear corrective glasses or not, but they are relatively subtle - However, once we move from the process of sensation to that of **perception**, or the interpretation of sensory input, individual differences become more evident - A stimulus is anything that elicits a reaction from our sensory systems. For example, we react to light energy that falls within our visual range, but we cannot see light energy that falls outside that range, such as the microwaves that cook our dinner or the ultraviolet waves that harm our skin - **Transduction:** the translation of incoming sensory information into neural signals - **Absolute threshold:** The smallest amount of stimulation that is detectable - **Difference threshold:** The smallest difference between two stimuli that can be detected - **Signal Detection:** Correctly identifying when a faint stimulus is or is not present - Once information from the sensory systems has been transduced into neural signals and sent to the brain, the process of perception, or the interpretation of the sensory information, begins. Perception allows us to organize, recognize, and use the information provided by the senses - Unfamiliar, changing, or high-intensity stimuli often affect our survival and have a high priority for our attention - To prioritize input, we use selective attention or the ability to focus on a subset of available information and exclude the rest - We refer to the brain's use of incoming signals to construct perceptions as **[bottom-up processing]** - In **[top-down processing]**, we use knowledge gained from prior experience with stimuli to perceive them - Gustav Fechner (1801--1887) developed methods, which he called **[psychophysics]**, for studying the relationships between stimuli (the physics part) and perception of those stimuli (the psyche or mind part) - The smallest possible stimulus that can be detected at least 50 percent of the time is known as the **[absolute threshold]** - **[difference threshold]**, or the smallest difference between two stimuli that can be detected at least 50 percent of the time (this is also referred to as a just-noticeable difference, or JND) - As stimuli get larger, differences must also become larger to be detected by an observer, a phenomenon known as Weber-Fechner Law - **signal detection** is a two-step process involving (a) the actual intensity of the stimulus, which influences the observer's belief that the stimulus did occur, and (b) the individual observer's criteria for deciding whether the stimulus occurred - **[Vision]**, the processing of light reflected from objects, is one of the most important sensory systems in humans. Approximately 50 percent of our cerebral cortex processes visual information, in comparison to only 3 percent for hearing and 11 percent for touch and pain - Visible light, or the energy within the electromagnetic spectrum to which our visual systems respond, is a type of radiation emitted by the sun, other stars, and artificial sources such as a light bulb - Wavelength, or the distance between successive peaks of waves, is decoded by our visual system as colour or shades of grey. The height, or amplitude, of the waves is translated by the visual system into brightness. Large-amplitude waves appear bright, and low-amplitude waves appear dim - Gamma rays, x-rays, ultraviolet rays, infrared rays, microwaves, and radio waves lie outside the capacities of the human eye - Toward the front of the eye, the outer covering becomes clear and forms the **[cornea]**. The cornea begins the process of bending light to form an image on the back of the eye - Directly behind the pupil and iris is the main optical instrument of the eye, the **[lens]**. Muscles attached to the lens can change its shape, allowing us to accommodate, or adjust our focus to see near or distant objects. The muscles relax and the lens flattens in order to focus on distant objects, and the muscles contract and the lens becomes more spherical to focus on near objects. Behind the lens is the main chamber of the eye, and located on the rear surface of this chamber is the **[retina]**, a thin but complex network of neurons specialized for the processing of light - Located in the deepest layer of the retina are specialized receptors, the rods and cones, that transduce the light information - Located in the deepest layer of the retina are specialized receptors, the rods and cones, that transduce the light information. However, before light reaches these receptors, it must pass through layers of blood vessels and neurons. We normally do not see the blood vessels and neural layers because of sensory adaptation. - adaptation occurs when sensory systems tune out stimuli that never change - Toward the middle of the retina is the **[fovea]**, which is specialized for seeing fine detail. When we stare directly at an object, the image of that object is projected onto the fovea. The fovea is responsible for central vision, as opposed to peripheral vision, which is the ability to see objects off to the side while looking straight ahead - The image projected on the retina is upside down and reversed relative to the actual orientation of the object being viewed - Rods are more sensitive to light than cones, and they excel at seeing dim light - Rods become more common as we move from the fovea to the periphery of the retina, so your peripheral vision does a better job of viewing dim light than your central vision does - Rods do not provide information about colour, nor do they provide clear, sharp images. - Cones function best under bright light and provide the ability to see both sharp images and colour - he primary colours of light are red, green, and blue, and mixing them together produces white light, like sunlight - **Trichromatic theory** is consistent with the existence of three types of cones in the retina that respond best to short (blue), medium (green), or long (red) wavelengths - An **[opponent process theory]** of colour vision does a better job than the trichromatic theory in explaining these colour afterimages. This theory proposes the existence of colour channels: a red--green channel and a blue--yellow channel. We cannot see a colour like reddish green or bluish yellow because the two colours share the same channel. The channels are "opponent" or competing. Activity in one colour group in a channel reduces activity in the other colour group - Infants as young as 2 days old appear capable of recognizing their mother's face - Although it is generally believed that face processing is a basic, universal visual function, cross-cultural research indicates that East Asians and Western Caucasians use different eye movement strategies while scanning faces. Eye-tracking shows that Western Caucasians focus on the eye and mouth regions of a face (reflective of a more locally focused, feature-based recognition strategy), while East Asians focus on the nose area (reflective of a more globally focused, face-centred recognition strategy - a group of German researchers known as the Gestalt psychologists tackled visual perception with a number of ingenious observations. The word *Gestalt* is derived from the German word for "shape." - These psychologists objected to efforts by Wilhelm Wundt and the structuralists to reduce human experience to its building blocks, or elements. Instead, the Gestalt psychologists argued that some experiences lose information and value when divided into parts - The Gestalt principle of continuity says that we perceive points forming a smooth line as belonging to the same object - To construct a 3D image, we use both **[monocular cues]** (one eye) and **[binocular cues]** (two eyes) - One of our most effective depth cues is **[retinal disparity]**. Because this cue requires the use of both eyes, we refer to retinal disparity as a binocular cue. Predator species, including ourselves, have eyes placed in the front of the head facing forward. As a result of this configuration, the visual scenes observed by the two eyes are different and overlapping, as shown in Figure 5.25. The differences between the images projected onto each eye are called disparities. These disparities do not tell us how far away an object is. Instead, they provide information about the relative distance between two objects in the visual field. As the distance between the objects increases, disparity increases - Older adults respond more slowly to changes in brightness, such as leaving a dark theatre into the sunlight. The muscles of the iris lose their elasticity, so pupils remain smaller, further reducing vision by limiting the amount of light that enters the eye - **Cornea:** bends light toward the retina - **Pupil:** forms an opening in the iris - **Lens:** Focuses light onto the retina - Sound begins with the movement of an object, setting off waves of vibration in the form of miniature collisions between adjacent molecules in air, liquid, or solids - in the case of sound, the height or amplitude of the wave is encoded as loudness or intensity and the frequency of the wave is encoded as pitch. High-amplitude waves are perceived as loud, and low-amplitude waves are perceived as soft. High-frequency waves (many cycles per unit of time) are perceived as high pitched, whereas low-frequency sounds are low pitched - Ultrasound can be used to clean jewellery or your teeth or to produce non-invasive medical images, Ultrasound stimuli occur at frequencies above the range of human hearing, beginning around 20 000 Hz - Infrasound refers to frequencies below the range of human hearing, or less than 20 Hz - fluids do a better job than air of transmitting sound waves - The components that make up the ear are divided into three parts: the outer ear, the middle ear, and the inner ear  - The pinna, the outer visible structure of the ear, collects and focuses sounds, like a funnel. In addition, the pinna helps us localize sounds as being above or below the head. Sounds collected by the pinna are channelled through the auditory canal, which ends at the tympanic membrane, or eardrum, at the boundary between the outer and the middle ear. The boundary between the middle and the inner ear is formed by another membrane, the oval window. The gap between these two membranes is bridged by a series of tiny bones. The purpose of these bones is to transfer sound energy from the air of the outer and middle ear to the fluid found in the inner ear. Sound waves are weakened as they move from air to water. When you try to talk to friends underwater, the result is rather garbled. Without the adjustments provided by these small bones, we would lose a large amount of sound energy as the sound waves moved from air to liquid - The cochlea is a complex structure, which is better understood if we pretend to unroll it. The cochlea may be divided into three parallel chambers divided from one another by membranes. Two of these chambers, the vestibular canal and the tympanic canal, are connected at the apex of the cochlea, or the point farthest from the oval window. Vibrations transmitted by the bones of the middle ear to the oval window produce waves in the fluid of the vestibular canal that travel around the apex and back through the tympanic canal. Lying between the vestibular and the tympanic canals is the cochlear duct. The cochlear duct is separated from the tympanic canal by the **basilar membrane**. Resting on top of the basilar membrane is the **organ of Corti**, which contains many rows of hair cells that transduce sound energy into neural signals. Each human ear has about 15 500 of these hair cells - **Organ of Corti**: A structure located on the basilar membrane that contains auditory receptors - **Basilar Membrane:** Membrane in the cochlea on which the organ of Corti is located. - As waves travel through the cochlea, the basilar membrane responds with a wavelike motion, similar to the crack of a whip. The movement of the basilar membrane causes the hair cells of the organ of Corti to move back and forth within the fluid of the cochlear duct. Bending the hair cells stimulates the release of neurotransmitters onto the cells of the **auditory nerve** - The basilar membrane needs to move very little before the hair cells are stimulated - hair cells stimulate axons forming the auditory nerve. One branch of each auditory nerve cell makes contact with the hair cells, while the other branch proceeds to the medulla of the brainstem. From the medulla, sound information is sent to the midbrain, which manages reflexive responses to sound, such as turning toward the source of a loud noise. In addition, the midbrain participates in sound localization, or the identification of a source of sound - The midbrain passes information to the thalamus, which in turn sends sound information to the primary auditory cortex, located in the temporal lobe. The primary auditory cortex conducts the first basic analysis of the wavelengths and amplitudes of incoming information - The frequency of a sound interacts with our perception of its loudness - By the age of 6 months, infants turn their heads in the direction of a loud or interesting sound. It is likely that their thresholds for sounds are nearly at adult levels by this age - By the age of 1 year, children should reliably turn around when their name is called - After the age of 30, most people cannot hear sounds above 15 000 Hz. After the age of 50, most people cannot hear above 12 000 Hz, and people older than 70 years have difficulty with sounds above 6000 Hz - Sine wave speech shows us how culture in the form of experience with language can shape perception, but in other instances, perception can shape culture - **[Somatosensation]** (*soma* comes from the Greek word for "body") provides us with information about the position and movement of our bodies, along with touch, skin temperature, and pain - people who have impaired pain reception often die prematurely because of their inability to respond to injury - somatosensory stimuli arise from within the body or make contact with its surface - we find the structures of the **[vestibular system]**, which provide us with information about body position and movement